Die for molding plastic pallets

ABSTRACT

A two part die for injection molding an integral plastic pallet having a load carrying top portion and a supporting bottom portion each formed by transversely spaced ribs of U-shaped cross section, the die comprising two die sections having each a plurality of spaced webs tapering toward free ends thereof and arranged with respect to each other so that when the die is closed the webs of one section will intermesh and engage without play plane side faces of the other section and so that at the free ends of the webs hollow spaces of U-shaped cross sections are formed for molding the U-shaped ribs.

United States Patent Ditges 1451 Oct, 24, 1972 [54] DIE FOR MOLDINGPLASTIC PALLETS [72] Inventor: Ernst Ditges, Herzebrock, Westfalen,Germany [73] Assignee: Press-Und Stanzwerk Paul Craemer KG, Herzebrock,(Westfalen), Germany [22] Filed: Feb. 8, 1971 [21] Appl. No.: 113,235

Related US. Application Data [62] Division of Ser. No. 785,812, Dec. 20,1968,

Pat. No. 3,603,272.

[30] Foreign Application Priority Data 1 Dec. 20, 1967 Germany.; ..P1556 151.0

[52] US. Cl ..249/142, 425/242 [51 Int. Cl. ..B28b 7/16 [58] FieldofSearch ..18/30 WM, 30 WC, 30 WN,

30 WP,l8/D1G. 58, 42 D, 44, 30 PM, 30 PT,

42 R, 34 R, 45 R, 30 WR, 30 WV, DIG. 8; 7 249/119, 120,l29,l30,132,154,160,145,

175, 142; 25/118 R, 41 G, 44, DIG. 24;

[56] References Cited UNITED STATES PATENTS 3,444,589 5/1969 Bowin....,...1s 1 9 A )g 1/1970 Passarelli 1,...l8/19 P X 3,597,800 8/1971Silverman ..18/19 P X 1,727,343 9/1929 Guyot ..249/ 145 X 1,029,488 6/1912 Burghoff et a1 ..18/44 3,502,767 3/ 1970' Morrison et a1 18/30 WN3,099,061 7/ 1963 Marchioli et a1 ..25/D1G. 24

Primary Examiner-Robert D. Baldwin Assistant Examiner-David S. SafranAtt0meyMichael S. Striker [57] ABSTRACT v A two part die for injectionmolding an integral plastic pallet having a load carrying top portionand a supporting bottom portion each formed by transversely spaced ribsof U-shaped cross section, the die comprising two die sections havingeach a plurality of spacedwebs tapering toward free ends thereof andarranged with respect to each other so that when the die is closed thewebs of one section will intermesh and engage without play plane sidefaces of the other section and so that at the free ends of the webshollow spaces of U-shaped cross sections are formed for molding theU-shaped ribs.

6 Claims, 7 Drawing Figures PATENTEDnm 24 m2 SHEET30F3 JW H v EnmrDifGar DIE FOR MOLDING PLASTIC PALLETS CROSS-REFERENCE TO RELATEDAPPLICATION The present invention is a divisional application of theapplication Ser.- No. 785,812 filed Dec. 20, 1968 with the title PLASTICPALLET AND DIE FOR PRODUCING THE SAME now U. S. Pat. No. 3,603,272.

BACKGROUND OF THE INVENTION Flat pallets are used in material handlingoperations. Such flat pallets have a top surface for placing a loadthereon and a bottom surface whichis equally flat. Spacing members arelocated between the top and bottom surfaces and such pallets have beenconstructed in the past of different designs and of wood. Woodenpallets, however, become easily damaged during severe handling and heavyloading, and as a result such wooden pallets have only a relativelyshort life span. In addition, wooden pallets are susceptible to theeffects of acids, alkalines, salts and humidity. Furthermore, wood is agood nutrient for the growth of bacteria. Therefore, wooden pallets arenot suitable for used in processes involving food supplies. The samealso applies to pallets made of steel, since they are'readilysusceptible to rust, even though their surfaces may be coated or plated.

Accordingly, flat pallets made of synthetic material, such as plastic,have recently been considered. The plastics preferably used for thispurpose are polyethyleneor polystyrene. Conventional plastic pallets asused in the art, however, have the disadvantage that they have to beassembled of a number of parts. As a result, such pallet assemblies arecostly to produce. In addition the load carrying capability andstability of the conventional plastic pallets leaves much to be desired.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a die for injection molding of integral plastic pallets having ahigh load carrying capacity. I Y It is also an object of the presentinvention to provide for a die of the aforementioned kind which issimple in construction and operation.

With these and other objects in view, the die according to the presentinvention for injection molding of a plastic pallet mainly comprises twocooperating die sections having faces facing each other and eachprovided on the respective faces with a plurality of webs spaced fromeach other in transverse direction. The webs on the face of one diesection project and taper toward the face of the other die section, andthe webs on the two die sections are arranged with respect to each otherin such a manner so as to intermesh free of play and so as to engageeach other along planar side faces when the die sections are closed andto form at their tapering ends U-shaped hollow spaces for moldingU-shaped ribs of the pallets in which the legs of the U- shaped ribsformed by the webs of one die section are directed toward the legs ofthe U-shaped ribs formed by the webs on the other die section to therebyprovide for a pallet having a top portion and a bottom portion spacedfrom each other and each formed by U-shaped ribs.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. ,Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side view of the undersideof the pallet, and is taken to one side of the axis of symmetry A-Awhich is a central axis;

FIG. 2 is a sectional view taken along the line IIII in FIG. 1; I

- FIG. 3 is a sectional view taken along the line IIIIII in FIG. 1;

FIG. 4 is a sectional view taken along the line IVIV in FIG. 1;

FIG. 5 is a partial top view of the interior side of an injection moldedportion for producing the pallet of the construction of FIGS. 1 to 4;and v FIGS. 6 and 7 show two different sections at right angles to thedie form members used in a die for injection molding of the pallet ofFIGS. 1 to 4, respectively taken along the line VI-VI and VIl-,VII ofFIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, FIGS.1 to 4 show the top surface of a pallet made of strong synthetic plasticmaterial such as hard polyvinylchloride or polyolefm. A plurality ofparallel profiled and U-shaped ribs 1 lie between rectangular recesses2. At the underside or set-on surface are, similarly, a plurality ofparallel profiled and U-shaped ribs 3 lying between rectangular recesses4. The ribs 1 and 3, as well as the recesses 2 and 4 of both surfacesare displaced in relation to each other. The arrangement is such thatthe ribs 1 of the top surface lie about the recesses 4 which have asomewhat wider dimension than the ribs 1. The ribs 3, at the same time,on the set-on surface or underside or placement surface are, at the sametime, beneath the recesses 2 which are similarly wider in width,to someextent, than the ribs 3. These dimensional relationships and arrangementmay be seen by referring to FIGS. 3 and 4.

Between the ribs 1 and 3, and at right angle to them, are vertical flatbridges 5 which serve as spacers. In addition, flat bridges 6 areprovided between legs of the U-shaped ribs 1 and 3 which liesubstantially vertically opposite to each other outside of the externalflat bridges 5. These flat bridges 6 also serve as spacers, and

when functioning together with the vertical flat spacers 5 of thepallet, an exceptionally large amount of stability is realized.

The top surface, the placement surface and the flat bridges 5 and 6 areof integral construction and produced through injection molding as aone-piece unit, in accordance with the present invention.

The top surface has a frame 7 which extends beyond all of the sides ofthe placement surface. This frame 7 has a U-shaped profile similar tothe ribs 1 and 3. As shown in FIGS. 3 and 4, angle or U structuralmembers 8 may be injection molded into this frame. These structuralmembers 8 serve to impart additional stability to the tray or pallet. Itis also possible to injection mold similar such structural members intothe ribs 1 and/or 3. These structural members may be made of iron orother metallic substance.

Holes 9 are provided in the ribs 3 of the placement surface. These holesprevent the accumulation of water or other fluids in the upper openprofiles of these ribs."

The placement surface also has four large rectangular recesses 10 whichare intended for receiving the running rollers of fork-lift trucks. Thelegs of the U- shaped ribs 3 bordering the recesses 10 are maintainedsomewhat flater and inclined, so that driving in and out of the palletsby fork-lift trucks is simplified.

- The dies for producing the pallets with the structure described above,consists of two parts 11 and 12, as shown in FIGS. 6 and 7. Both dieparts have form members or webs 13 or 14 with plane side surfaces attheir inner surfaces and spaced from each other, while at the same timeprojecting toward each other. The members 13 and 14 are displaced inrelation to each other so that when the die is .-closed, the membersreach into each other without play. Hollow spaces 15 and 16 only remainfor the purposesof forming the plastic ribs 1 and 3. These hollow spaces15 and 16 remain at the outer ends of reduced cross section of themembers 13 and 14, and are U-shaped. Between neighboring front surfacesof the membe 13 and 14, free gaps 17 are provided for forming thevertical plastic bridges 5 which are at right angle to the ribs 1 and 3.These bridging members such as the member 5, for example, may also bedesignated as cross members or flange members. A number of members 13and 14 lying outside of the outer gap 17, furthermore, are designed sothat a free gap 18 remains for thepurpose of forming the plastic crossmember 6, after the die parts 11 and 12 are brought together. The

members 13 have, moreover, pins 19 on their outer surfaces, for thepurpose of forming holes 9 in the plastic ribs 3.

The recesses 10 serving the purpose of receiving the running rolls ofthe fork-lift truck are rectangular, and are formed through therectangular forming member 20 in the die part 12.

The flat pallets made of synthetic or plastic material, in accordancewith the present invention, are preferably produced with dimensions of1,000 X 1,200 mm, 800 X 1,200 mm, and 800 X 1,000 mm. By using identicaldie elements, these sizes of pallets can be produced in integral orone-piece form through injection molding techniques.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied inplastic pallets and their dies, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

What is claimed as new and desired to be protected by Letters Patent is:

1. A die for injection molding of plastic pallets having a top portiondefining a plane top surface for carrying a load to be applied tothe'pallet, a bottom ortion de imng a plane bottom surface forsupporting e pallet, and spacing portions between said top and bottomportions and wherein the top and bottom portions are formed bysubstantially parallel U-shaped ribs, arranged spaced from each other toform recesses between said ribs and in which the ribs and recesses ofthe top portion are displaced relative to those in the bottom portion sothat the ribs of the top portion lie over the recesses of the bottomportion and the ribs of the bottom portion lie beneath the recesses ofthe top portion, said die comprising two cooperating die sections havingfaces facing each other and each provided on the respective face with aplurality of webs spaced from each other and projecting towards the faceof the other die section, each of said webs having a pair of planar sidefaces and a pair of planar end faces and a free end of reducedcross-section, said webs being arranged in a plurality of adjacent andparallel rows with the end faces of the webs in adjacent rows spacedfrom and facing each other to define a gap therebetween for formingvertical cross portions extending normal to the ribs of the pallet to bemolded and between the top and bottom portions thereof, the webs on saidtwo die sections being arranged in each row with respect to each otherso that-the webs on said two die sections intermesh free of play whensaid sections are closed and so as to form between said free ends of thewebs on one die section and the adjacent webs on the other die sectionelongated spaces of U-shaped cross-section for forming said ribs of saidpallet.

, 2. A die as defined in claim 1, wherein some of the side faces of thewebs located in the outermost rows of the plurality of rows arearranged'with respect to the side faces of adjacent webs to form, whenthe die sections are closed, a plurality of gapsbetween'said side facesfor forming cross portions parallel to and respectively extendingbetween the ribs of the top portion and corresponding ribs of the bottomportion.

3. A die as defined in claim 2, wherein at least some of said webs tapertoward said free ends thereof.

4. A 'die as defined in claim 1, wherein each of said webs is providedon the tapering end thereof with at least one projection extendingthrough said U-shaped space for forming an opening in the respective ribof the pallet.

5. A die as defined in claim 1, wherein each of the die sectionscomprises a plate and wherein each of said,

webs has an outer end portion wider than the remainder of the respectiveweb and abutting against the face of the respective plate, each of saidwider end portions having a side face abutting against the side face ofthe end portion of the adjacent web and said free end portion of reducedwidth of each of said webs on one die section ends short of thecorresponding outer end portions of the webs on the other die section,when the die is closed, so as to form said U-shaped space.

6. A die as defined in claim 5 and including a plurality of pinsprojecting from the free ends of the webs on one direction respectivelythrough the U-shaped spaces in engagement with the wider end portions ofrespective webs on the other die section.

1. A die for injection molding of plastic pallets having a top portiondefining a plane top surface for carrying a load to be applied to thepallet, a bottom portion defining a plane bottom surface for supportingthe pallet, and spacing portions between said top and bottom portionsand wherein the top and bottom portions are formed by substantiallyparallel U-shaped ribs, arranged spaced from each other to form recessesbetween said ribs and in which the ribs and recesses of the top portionare displaced relative to those in the bottom portion so that the ribsof the top portion lie over the recesses of the bottom portion and theribs of the bottom portion lie beneath the recesses of the top portion,said die comprising two cooperating die sections having faces facingeach other and each provided on the respective face with a plurality ofwebs spaced from each other and projecting towards the face of the otherdie section, each of said webs having a pair of planar side faces and apair of planar end faces and a free end of reduced cross-section, saidwebs being arranged iN a plurality of adjacent and parallel rows withthe end faces of the webs in adjacent rows spaced from and facing eachother to define a gap therebetween for forming vertical cross portionsextending normal to the ribs of the pallet to be molded and between thetop and bottom portions thereof, the webs on said two die sections beingarranged in each row with respect to each other so that the webs on saidtwo die sections intermesh free of play when said sections are closedand so as to form between said free ends of the webs on one die sectionand the adjacent webs on the other die section elongated spaces ofU-shaped cross-section for forming said ribs of said pallet.
 2. A die asdefined in claim 1, wherein some of the side faces of the webs locatedin the outermost rows of the plurality of rows are arranged with respectto the side faces of adjacent webs to form, when the die sections areclosed, a plurality of gaps between said side faces for forming crossportions parallel to and respectively extending between the ribs of thetop portion and corresponding ribs of the bottom portion.
 3. A die asdefined in claim 2, wherein at least some of said webs taper toward saidfree ends thereof.
 4. A die as defined in claim 1, wherein each of saidwebs is provided on the tapering end thereof with at least oneprojection extending through said U-shaped space for forming an openingin the respective rib of the pallet.
 5. A die as defined in claim 1,wherein each of the die sections comprises a plate and wherein each ofsaid webs has an outer end portion wider than the remainder of therespective web and abutting against the face of the respective plate,each of said wider end portions having a side face abutting against theside face of the end portion of the adjacent web and said free endportion of reduced width of each of said webs on one die section endsshort of the corresponding outer end portions of the webs on the otherdie section, when the die is closed, so as to form said U-shaped space.6. A die as defined in claim 5 and including a plurality of pinsprojecting from the free ends of the webs on one direction respectivelythrough the U-shaped spaces in engagement with the wider end portions ofrespective webs on the other die section.